Do Ink Green Screen is the best app for Green Screen out there. There is a cost to it but if you can get it, it is totally worth it. If you can't then I recommend iMovie but you have so many more features with Do Ink and the quality of the green screen effect is higher. Highlighted features include adding 2 layers of green screen on top of your video, a colour wheel which means your background doesn't have to be green, it could be blue, red, purple etc and the masking tool which removes anything in your video or background image that you don't want. Transport your children to any place on or off the planet with this amazing app!